In a first aspect, this invention relates to a machine intended for chip cutting machining, in particular metalworking, of the type that comprises one or more cutting tools with a front part, which has at least one cutting insert, as well as a rear part, which is detachably fixed in a permanent holder in the machine, the tool including a plurality of nozzles, which have the purpose of spraying jets of high pressure cooling liquid towards the cutting insert and which are supplied with pressurised cooling liquid from at least one liquid supply source, more precisely via a system of ducts inside the tool.
The practice of cooling not only the cutting inserts of a cutting tool, e.g. tools for turning, but also the workpiece commonly consisting of metal which is machined by the tool has been known for a long time. A primary aim of today""s technology for cutting or chip cutting machining is to enable use of as high a pressure as possible for the cooling liquid and to supply this in the form of one or more fine jets tightly focussed together, in the main directed towards the cutting insert and the chip released thereof. The higher the pressure which may be used in the liquid jet, the greater are the possibilities to use the liquid jet, in an advantageous way, not only for pure cooling, but also to mechanically effect the chip released from the work piece (by applying a force from the jet on the chip) more precisely with the purpose of breaking up the chip into smaller pieces and/or guiding the chip away from the tool in a controlled manner. Among those skilled in the art, there are different opinions about what in this connection is to be regarded as low and high liquid pressure, respectively. Generally, the classification could, however, be made in the following intervals:
Low pressure less than 10 bar,
Intermediate pressure 10-100 bar, and
High pressure greater than 100 bar
The present invention relates essentially to high pressure liquid cooling technology, more precisely to the usage of a plurality of nozzles in the individual cutting tool.
A cutting tool for machines of the type mentioned initially has been disclosed previously in WO 99/39852. In this case, the tool includes a plurality of nozzles, one of which consists of a low pressure liquid nozzle, while a set of two or more nozzles consists of high pressure liquid nozzles. The low pressure liquid nozzle is supplied with cooling liquid from a separate liquid supply source in the machine, more precisely via a duct which extends through the tool, as well as through a clamping unit co-operating with the tool, which is fixedly mounted in the machine and which serves as a holder in which the tool may be detachably mounted. The high pressure liquid nozzles communicate with another liquid supply source via another, separate duct which extends through the clamping unit and the tool, more precisely up to a cavity common for all high pressure liquid nozzles inside the tool. In practice, this cavity is formed at the rear side of a detachable plate in which the high pressure liquid nozzles are mounted. The fact that the duct for the supply of high pressure cooling liquid to the high pressure liquid nozzles exhausts into a space common for these nozzles means, in practice, that all high pressure liquid nozzles are activated when the cooling liquid is supplied to the common space. In other words, all high pressure liquid nozzles will, simultaneously, spray out towards the cutting insert a number of jets corresponding to the number of nozzles. These jets may be given different points of impact on the cutting insert thanks to the fact that the nozzles are adjustable in different positions.
Development work performed recently, which is the basis for the present invention, has shown that the direction of the individual high pressure liquid jets in relation to the edge of the cutting insert is of importance not only for the cooling effect, but above all for the possibilities to break up and/or guide the released chip in an optimal way. More precisely, it has been established that optimal results in respect of cooling and chip guiding, respectively, are obtained if the high pressure liquid jet is directed perpendicularly to the edge (on quadrangular cutting inserts to each straight edge and on round cutting inserts 90xc2x0 to the tangent at arbitrary points along the endless edge). From the right angle, the cooling and chip guiding effects decrease more and more the more acute the jet angle is, to a point when the angle approaches zero. However, when this insight into the importance of the jet angle is to be put into practice, a phenomenon which is difficult to master presents itself, viz. the fact that the operative part of a cutting insert may xe2x80x9cmigratexe2x80x9d during a machining operation. Thus, during copy turning, for instance, initially one and then the other edge on a quadrangular cutting insert may be active when the cutting insert follows a path of movement with varying depths of cut in the workpiece. With round cutting inserts having an endless edge, a limited, active portion of the edge is transported backwards and forwards along the edge depending on the pattern of movement of the cutting insert during the machining operation.
Although the high pressure liquid nozzles which are included in the cutting tool known from WO 99/39852 are adjustable in different positions in order to direct the high pressure liquid jets to different points of impact on a cutting insert, this tool is not suitable for mastering the above-mentioned migration phenomenon. During operation, the nozzles are thus adjusted in given, fixed positions, the jets being sprayed out simultaneously from all nozzles. If the individual nozzles were to be adjusted with the purpose of attaining the largest possible angle relative to the edge, i.e. an angle as close to 90xc2x0 as possible, there is an obvious risk that the jets would intersect each other. This is something that would imply that tightly concentrated and focussed jets would not reach the cutting edge, but rather collide in a cascade before that. On the other hand, if the nozzles were to be installed in such a way that the risk of collision was obviated, the angle between the individual jet and the cutting edge would necessarily become less.
The present invention aims at solving the above-mentioned problems and at providing an improved machine as well as an improved cutting tool for machines of the kind in question. Therefore, a primary object of the invention is to provide a cutting tool by means of which high pressure cooling liquid jets may be directed at one or more cutting edges on one and the same cutting insert while achieving a jet angle, which for each given geometry is optimally independent of which edge portion that is active during a machining operation. Another object is to create a cutting tool on which the greatest possible cooling and chip breaking effect, respectively, may be attained while at the same time reducing the cooling liquid consumption to a minimum. It is also an object to provide a structurally simple cutting tool, which may be adjusted in a reliable way in respect to the spraying of the cooling liquid during operation.
According to the invention, at least the primary object of the cutting tool is attained by the features defined in the characterizing clause of claim 4. A preferred embodiment of the cutting tool according to the invention is furthermore defined in the dependent claim 5.
In addition to the cutting tool as such, the invention also relates to a machine, intended for chip cutting machining, of the type that may include one or more cutting tools of the kind in question. Features of the machine according to the invention are seen in the characterizing clause of claim 1. Preferred embodiments of the machine according to the invention are furthermore defined in the dependent claims 2 and 3.
As regards the two categories of claims which have been made, it should be pointed out that separate cutting tools for machines for chip cutting machining are commonly manufactured and distributed by certain manufacturers, while the machines as such, i.e. excluding the cutting tools, are manufactured and distributed by other manufacturers, who purchase the tools from the first-mentioned manufacturers and mount the tools in the machines in connection with final delivery. However, in exceptional cases, it may also occur that one and the same manufacturer manufactures the machines as well as the cutting tools included therein.
It has been known previously per se to form such tools which comprise two or more spaced-apart cutting inserts, with a number of cutting inserts corresponding to the number of nozzles, which are supplied with cooling liquid via separate ducts and which may be activated one at a time by the fact that all ducts except one are shut. However in this case, the individual nozzle is adjusted to direct the liquid jet towards one single, given point on the co-operating cutting insert.